1. Field of the Invention
This invention relates to a stabilized synthetic polymer composition comprising (1) a synthetic polymer, (2) as a stabilizer, a poly(alkylated alkenylphenol) of a specific formula and (3) as an auxiliary stabilizer, a specific organic sulfur compound or an organic phosphite compound.
2. Description of the Prior Art
It is known that synthetic resins such as polyethylene, polypropylene and polyvinyl chloride are susceptible to deterioration by oxygen on exposure to air or at high temperature. It is also known that this deterioration leads to a coloration of the synthetic resins or reduces their mechanical strength, and the resins become useless. Hence, a great need exists for antioxidants which protect these synthetic resins from deterioration by oxidation, and various antioxidants have been added to synthetic resins in the past. Of the antioxidants thus-far used, phenolic antioxidants such as 2,6-di-tert.-butyl-p-cresol and butylidene bis-2-tert.-butyl-5-methylphenol have a great effect, and are widely used.
However, these phenolic antioxidants have the defect that they volatilize during processing at high temperatures, are easily extracted from the resins by water, oils, etc., or color the resins. Consequently, they can be used to stabilize the resins only for short periods of time. To remedy these defects, attempts have been made to increase the molecular weight of the stabilizers, and a low-molecular-weight condensate of phenol and formaldehyde has been suggested. However, since these compounds, have a low stabilizing effect, and greatly color the resins, they are not suitable for practical applications.
British Pat. No. 971,753 discloses the addition of a poly(alkylated alkenylphenol) as an antioxidant to rubber. However, the poly(alkylated alkenylphenol) does not have a high stabilizing effect when it is added alone to rubber or a resin.